KB909: Track Voltage Measurement on DCC Layouts with Direct Home Wiring

This article was last updated on Oct. 25, 2010, 2:19 p.m. | Print Article | Leave Feedback



Track voltage on DC (analog) layouts can be measured from rail to rail.  However, with DCC layouts that use direct home wiring as recommended by Digitrax, this method of measurement does not work with most voltmeters.

Track voltage (output from the booster to the rail) on DCC layouts with
direct home wiring can be measured as follows:

1.     With the system powered up and with the TRACK STATUS LED on, use your throttle to select the analog address 00 and set the speed to 00.

2.     With a multimeter set to the 20 volt DC scale, measure the voltage from RAIL A to ground (you can use the SCALE or MODE toggle switch body, the case screw on the back, or the GROUND terminal on the front of the booster as ground for this measurement).  Repeat this measurement from RAIL B to ground.

3.     Total track voltage is the sum of the voltage measurements from RAIL A to ground & RAIL B to ground.

4.     The difference between the RAIL A & RAIL B voltages should not exceed 0.2 volts.  Satisfactory operation will still occur if the difference is as much as 0.5 volts.

5.     Track voltage can be adjusted by using the trim pot inside the booster located between the LOCONET B port and the SCALE switch.  This is useful for balancing the track voltage between power districts.

6.     If you find that the track voltage on one of your boosters falls outside these ranges, be sure that there are no analog addresses running in the system by using your throttle to select the analog address 00 and setting the speed to 00.  Once you have done this, re-measure the voltages.  

If you find that there is still a problem, contact Digitrax customer support at (850) 872-9890, during normal business hours M-F, US Central Time, or e-mail techsupport@digitrax.com

Track Voltages should be approximately (depending on trim pot adjustments you have made):

SCALE Switch setting

RAIL A to ground voltage

RAIL B to ground voltage

Total track voltage

N

  6.2 (+/-0.25v)

  6.2 (+/-0.25v)

12.4  (+/-0.5v)

HO

  7.5  (+/-0.3v)

  7.5  (+/-0.3v)

15.0  (+/-0.6v)

O/G

10.0  (+/-0.5v)

10.0   (+/-0.5v)

20.0  (+/-1.0v)

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